Communications equipment must typically be tested in order to verify proper performance. Such testing can include, for example, development testing, wherein proper functioning of a prototype of a candidate design is verified; acceptance testing, where it is confirmed that an individual component or piece of equipment functions according to specifications; or ongoing field tests, where correct functioning of equipment in the field is monitored. Such testing may be performed, for example, by external test equipment or by built-in self-test (BIST) capability.
One manner of testing communications equipment is to subject the equipment to test patterns that simulate the type of data that the equipment will be handling in use. For example, Fibre Channel Framing and Signaling draft standard FC-FS Rev. 1.80 is a proposed American National Standard for Information Technology. A Fibre Channel jitter tolerance pattern formed by framing an 8b10b encoded random jitter test pattern into a standard frame can be employed with respect to applications of the aforementioned standard. Some types of communications equipment, for example, serializer/deserializers, may have multiple receiver latches. If conventional test techniques are employed with such equipment, each latch may only be exposed to a static pattern, and thus only static mono failure of the given latch may be detected.
Accordingly, it would be desirable to provide an apparatus and method where test patterns can be offset in successive frames, such that more failure modes can be detected than with a test technique where offset is not employed, for equipment having multiple receiver latches, and other equipment that can benefit from pattern offset.